According to a study by The Wall Street Journal of 101 apps they looked, at 56 of them divulged unique IDs to third party companies without the user's permission. This practice takes place not only with Android apps, but also iPhone apps.
Believe it or not, 47 of the apps studied actually sent your phone's location! Five of the apps also sent users' gender, age, and other personal traits. Pandora, a very popular radio app with both Android and iPhone users is reported to send age, gender, location, and phone identifiers to numerous ad networks. Paper Toss for Android is revealed to have sent your phone ID number to at least five ad companies.
DoodleJump and the popular Angry Birds games were exposed to be communicating the user's screen name or password to advertisers. This is extremely dangerous as the information could be used to jeopardize poorly passworded accounts.
Smartphone users do not have the same available options like PC users, who can block or delete tracking cookies. In conclusion, the options available to smartphone users at the moment are to tolerate this, or don't use the apps.
Source: The Wall Street Journal